Variable head compressor



y 1962 H. .A. GREENWALD 3,

VARIABLE HEAD COMPRESSOR Filed June 1, 1959 2 She ets-Sheet 1 INVENTORZ HAROLD A. GREE/VWALD,

W y w Affa r/lay.

July 3, 1962 H. A. GREENWALD 4 VARIABLE HEAD COMPRESSOR Filed June 1, 1959 2 Sheets-Sheet 2 INVENTOR. HAROLD A. GREENWALD Agenl.

ite States Patent 3,042,221 VARIABLE HEAD (IQMPRESSOR Harold A. Greenwald, Los Angeles, Calitl, assignor to The Garrett Corporation, Los Angeles, Calif., a corporation of California Filed June 1, 1%), Ser. No. 817,264 6 Claims. (Cl. 23t)--114) This invention relates to a centrifugal compressor in which the head or change in pressure through the compressor may be regulated in accordance with load requirements without changing the speed of rotation of the compressor, and has for its object the provision of simple and effective means for imparting a pre-swirl to the elastic fluid or gas at the compressor inlet to vary the pressure change through the compressor.

In the operation of centrifugal compressors, it is often desired to operate at constant speed while varying the compressor head in accordance with load requirements, without changing compressor speed or starting and stopping the compressor. In other cases, it may be desired to maintain a constant head or pressure change through the compressor irrespective of variations in the speed of rotation of the compressor. Both of these results can be obtained by imparting a pre-swirl or rotative movement to the fluid drawn into the impeller of the compressor and according to this invention, such pre-swirl is created either in the direction of rotation of the compressor impeller or in contra-rotation thereto, by displacing the axis of an inlet duct to either side of the axis of rotation of the compressor impeller to effect a pre-swirl in the desired direction.

The amount of pre-swirl or rotative movement imparted to the fluid prior to its entrance into the impeller will depend upon the amount the inlet duct axis is displaced relative to the axis of the impeller. With the duct axis displaced so that the greater amount of inlet fluid is moving in the direction of rotation of the impeller, pre-swirl of the fluid will be in the same direction as the impeller rotation and the head or pressure change through the compressor will be lowered. Conversely, with the axis of the inlet duct displaced on the opposite side of the impeller axis to that recited above, the direction or pre-swirl will be opposite to the direction of rotation of the impeller and the pressure change through the compressor will be increased.

Another advantageous effect of the pre-swirl imparted to the inlet fluid according to this invention is the lessening of the tendency of the compressor to surge or hammer because oflight loads and low flow, where such surging or hunting would otherwise manifest itself in a backflow of fluid into the impeller to adversely eflect the efficiency of operation of the unit.

It is therefore an object of the invention to provide an improved and simplified means for imparting a pre-swirl or rotative movement to fluid being drawn into the impeller of a centrifugal compressor prior to the entrance of the fluid into the impeller.

Another object of the invention is the provision of means for varying the pressure change in a centrifugal compressor for imparting a pre-swirl to the fluid in the compressor inlet by displacing the axis of the inlet duct leading to the compressor inlet relative to the axis of the compressor impeller.-

Another object of the invention is the provision of a variable head compressor in accordance with the preced ing object where the displacement of the duct axis is varied in accordance with the value of a condition reflecting the compressor output.

A further object of the inventtion is a variable head compressor in accordance with each of the preceding objects in which the displacement of the duct axis relative 3,042,291 Patented July 3, 1962 to the axis of the impeller may be effected at opposite sides of the impeller axis to effect a pre-swirl rotation in opposite directions to increase or decrease the pressure change through the compressor as desired.

Other objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended drawing illustrating certain preferred embodiments in which:

FIG. 1 is a schematic, horizontal sectional view through a variable head compressor according to this invention;

FIG. 2 is a vertical sectional view taken on line 22 of FIG. 1;

FIG. 3 is a vertical sectional view taken on the line 3-3 of FIG. 2;

FIG. 4 is a plan view schematically illustrating one mode of control for a variable head compressor according to the invention;

FIG. 5 is a cross-section of a portion of a compressor outlet duct illustrating the installation of a temperature sensing bulb therein;

FIG. 6 is a cross-section similar to FIG. 5 illustrating the connection of a pressure tap in a compressor outlet duct; and

FIG. 7 is a plan view similar to FIG. 4 illustrating another mode of control for a variable head compressor according to the invention.

The compressor of this invention is illustrated in the drawing generally at 1 having a casing 2 with an inlet 3 and an outlet scroll 4. Within the casing 2 is a conventional centrifugal impeller 5 rotated by a shaft 6 and discharging into said outlet scroll 4 and thence into a suitable outlet duct 10. The upper portion of the casing 2 is shown flanged at 7 about the inlet 3 and welded or otherwise secured to the flange 7 is a plate 8 having an inlet opening 9 therein co-axial and co-extensive with the inlet 3. An inlet duct 11 is disposed substantially at right angles to the axis of the shaft 6 and impeller 5 and is composed of a stationary portion 12 and an arcuately shiftable portion 13 connected thereto by a flexible sleeve 14. At the free end of the duct portion 13 is a swirl chamber 15 having an arcuate length transversely of the duct portion substantially twice the diameter of the inlet 3, being thus convex outwardly at 16 and 17 with radii substantially the same as the radius of the inlet 3. The swirl chamber 15 has a bottom opening of arcuate form having its length substantially equal to the width of the chamber 15, being twice the diameter of the inlet 3 and having a width equal to the inlet diameter.

The closed end of the swirl chamber 15 is of smooth arcuate form as at 18 to assist in the imparting of a swirling movement to the inlet gas and is provided with an exterior finger 19 connected by a link 21 to an operating rod 22 connected to be operated by a pressure bellows 23 disposed within a stationary casing 24 and loaded by a spring 25. The interior of the bellows 23 is connected by a tube 26 to a pressure source, such as a pressure on the outlet side of the compressor or to a temperature bulb responsive to the temperature of a medium reflecting the load on the compressor. The swirl chamber 15 is mounted to slide easily over the sealing plate 8 as by a flanging arrangement shown schematically at 27, there being provided a fluid tight seal between the swirl chamber 15 and plate 8 as indicated at 2-8.

In FIG. 1, the inlet duct portion 13 is shown in full lines in position with the longitudinal axis of the duct passing through the central axes of inlet .3 and impeller 5. In this position, the amounts of fluid or gas passing through the inlet at opposite sides of the impeller and inlet axis are balanced so that no pre-swirl rotation is imparted to the fluid in the compressor inlet. In this position, the inlet fluid passing through the horizontal inlet c annel duct 11 will move downwardly into the vertical cornpressor inlet 3 and into the impeller passages without rotating prior to its entrance into the impeller.

In the dotted line showing of FIG. 1, the inlet duct portion 13 has been rotated or shifted to its maximum displaced position to the right, where the inlet 3 indexes with the convex portion 16 of the swirl chamber 15 and the axis of the inlet duct is displaced to be substantially tangential to the inlet 3. It is thus seen that the inlet fluid is grealy unbalanced with respect of the axis of the compressor inlet and impeller, and accordingly, the inlet fluid or gas will be given a clockwise rotation and will spiral downwardly as it changes direction from the horizontal axis of the duct 11 to the vertical axis of the compressor inlet. If the impeller 5 is also rotating in a clockwise direction, the eifect of the rotation imparted to the fluid in the same direction will be to lower the head or change in pressure through the compressor. Thus it will be apparent that the amount and direction of preswirl imparted to the inlet fluid, and hence the change in pressure occurring across the impeller 5, may be controlled by varying the position of the swirl chamber 15 relative to the compressor inlet 3.

The position of the bellows 23, and its rod 22 and swirl chamber 15 will be such as to effect a balance between the force exerted by the pressure within the bellows 23 and the force exerted by the spring 25 and the amount of pre-swirl imparted to the inlet fluid, and hence the variation in change of pressure through the compressor, will be determined by the distance the inlet duct is moved and the displacement of the duct axis relative to the axis of the duct inlet and impeller. As stated, this pressure regulator represented by the bellows 23 and its balancing spring 25 may be subject to a pressure on the discharge side of the compressor as shown in FIGS. 4 and 6, or to a pressure resulting from a temperature bulb 3%? as shown in FIG. 5, or to another condition reflecting or influenced by the compressor output as shown in FIG. 7, or to any other condition in response to which it is desired to vary the compressor head.

The above description of the effect of displacement of the axis of the inlet duct to the dotted line position at the right of FIG. 1 will operate with reverse effect if the displacement is effected to the left of the full line position. In this latter condition, the p-re-swirl or rotation imparted to the inlet gas will be such as to cause a downward spiral within the inlet having counterclockwise rotation, so that the inlet fluid enters the impeller with a rotative motion opposite to the direction of rotation of the impeller with a resulting increase in the head or pressure change through the compressor.

The pre-swirl producing arrangement may be advantageously applied in any system utilizing a centrifugal compressor where the compressor is acting on any elastic fluid such as various gases including air, and as such, has particular applicability with respect to refrigeration systems, although obviously not limited thereto.

While a certain preferred embodiment of the invention has been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation consistent with the prior art.

What is claimed is:

l. A variable head compressor comprising: a housing having an inlet and an outlet; a centrifugal impeller within said housing adapted to draw a fluid into said inlet and discharge the same through said outlet; an inlet duct adapted to feed fluid to said compressor inlet and having its axis angularly disposed with respect to the rotational axis of the impeller, the end of said duct adjacent to said compressor inlet defining a swirl chamber supported for transverse displacement relative to said inlet, said chamber being shaped so as to impart a swirl in one direction to said fluid when displaced to one side of said inlet and a swirl in the opposite direction when displaced to the other side of said inlet and being provided with an outlet port registerable with said compressor inlet throughout the range of said displacement, and actuator means operable to displace said chamber relative to said inlet thereby to control the direction and amount of pre-swirl imparted to said fluid.

2. A variable head compressor comprising a housing having an inlet and an outlet, a centrifugal impeller within said housing and adapted to draw a fluid into said inlet and discharge the same through said outlet, an inlet duct adapted to feed fluid to said compressor inlet and having its axis angularly disposed with respect to the axis of the impeller, the end of said duct adjacent to said compressor inlet defining a swirl chamber supported for transverse displacement relative to said inlet, said chamber being shaped so as to impart a swirl in one direction to said fluid when displaced to one side of said inlet and a swirl in the opposite direction when displaced to the other side of said inlet and being provided with an outlet port :registerable with said inlet throughout the range of said displacement, and actuator means operable to control the displacement of said chamber in accordance with a condition reflecting the output of said compressor.

3. A variable head compressor which comprises: a housing having an inlet and an outlet; an impeller mounted for rotation within said housing to draw an elastic fluid into said inlet and discharge said fluid through said outlet; a duct feeding fluid to said compressor inlet and including a swirl chamber supported for transverse displacement relative thereto, the axis of said duct being angularly disposed with respect to the axis of said impeller; and means for displacing the axis of said duct transversely of said impeller axis for varying the swirl imparted to the fluid in said inlet, thereby to vary the pressure change through the compressor.

4. A variable head compressor which comprises: a housing having an inlet and an outlet; a centrifugal impeller within said housing drawing an elastic fluid into said inlet and discharging said fluid through said outlet; a duct feeding fluid to said compressor inlet and including a swirl chamber supported for transverse displacement relative thereto, the axis of said duct being angularly disposed with respect to the axis of said impeller; and pressure responsive means operatively connected with said duct for imparting movement thereto transversely of the axis of said impeller to displace said swirl chamber relative to said impeller axis in proportion to the pressure applied to said means, said displacement being effective to control the swirl imparted to the fluid entering the compressor inlet for varying the pressure change through the compressor.

5. A variable head compressor which comprises: a housing having an inlet and an outlet; a centrifugal impeller within said housing drawing an elastic fluid into said inlet and discharging said fluid through said outlet; a. duct feeding fluid to said compressor inlet, the longitudinal axis of said duct being angularly disposed with respect to the rotational axis of said impeller, the end of said duct adjacent said compressor inlet including a swirl chamber having an outlet indexing with said compressor inlet and forming a transversely movable fluidtight joint therewith, said swirl chamber outlet extending transversely of the duct beyond said inlet so as to index therewith when said chamber is displaced to either side of said inlet; and means for displacing said duct axis transversely of said impeller axis thereby to shift said swirl chamber transversely of said inlet.

6. A variable head compressor which comprises: a housing having an inlet and an outlet; a centrifugal impeller within said housing drawing an elastic fluid into said inlet and discharging said fluid through said outlet; a duct feeding fluid to said compressor inlet, the axis of said duct being angularly disposed with respect to the axis of said impeller, said duct including a swir chamber having an outlet indexing with said compressor inlet and forming a transversely movable fluid-tight joint therewith, said swirl chamber outlet extending transversely of said duct to either side of said inlet so as to index therewith When said chamber is displaced trans- Versely of said inlet to impart a pre-swirl to the fluid entering said inlet; and actuator means operatively connected with said duct and operable in response to a condition reflecting the compressor output for varying said displacement in accordance With variations in said condition, thereby to regulate the pressure change through said compressor.

References Cited in the file of this patent UNITED STATES PATENTS Gregory et a1. Dec. 7, 1943 Murphy Sept. 6, 1960 FOREIGN PATENTS Great Britain Apr. 9, 1934 France May 19, 1922 Germany Aug. 3, 1953 

